The present invention relates in general to devices for preventing silt and debris from collecting in storm water drainage pipes at construction sites, and in particular to a device that fits over and encloses the open end of a storm sewer drop inlet so as to trap and prevent silt and other debris from being washed into or being otherwise deposited within the inlet and thus the drainage pipes, while still enabling water to drain into the inlet.
In the construction of new housing and other types of developments, the road system generally is first marked out and the streets into and through the development are cut and graded. Thereafter, the storm water drainage system for the development is constructed, which typically includes the underground drainage pipes, collection boxes and culverts, and drop inlets that form the manholes or drain openings along the street. The culverts are installed after the street bed has been graded to the elevation, whereupon the drop inlets are then installed and connected to the culverts and to the collection boxes. The drop inlets generally are substantially cylindrical concrete pipes that are installed vertically, with their lower ends connecting to the collection boxes and drainage pipes, and their upper ends being substantially at street level.
Once the grading of the street bed has been completed and the drainage system substantially installed, the drainage system then will be buried and the curbs for the street are graded and poured. Thereafter, throats are provided for the manholes, the throats being poured about the open ends of the drop inlets to form the curb inlets or drains and manholes along the sides of the streets through which storm water drains.
During the construction of roads and drainage systems, until the street has been substantially completed and the curbs and throats of the sewer system have been poured, the drainage pipes and inlets must be kept substantially free of dirt and debris pursuant to state and county building codes. Keeping dirt and debris out of the drainage system is, however, very difficult to accomplish as once the curbs are graded and the roads completed, during grading of the curbs as well as additional grading on site, dirt and debris is pushed to the sides of the street by the motor grader or bulldozer, and thus may pass into the open upper ends of the drop inlets. In addition, rain, runoff and wind also tend to wash or blow dirt and debris into the open ends of the drop inlets, which then collects in the collection boxes and sewer pipes.
If dirt and debris are washed into or otherwise collected within the collection boxes and/or other parts of the drainage system, it becomes necessary to send laborers down into the drop inlets and collection boxes to manually clean out the dirt and/or debris that has been washed or accidentally dropped into the drainage pipes to comply with building code regulations. Such cleaning operations are difficult as the pipes are somewhat cramped, making it difficult to maneuver, and there is also the danger of cave-ins or collapse of the dirt, etc. that has built up around the sides of the drop inlets, creating a significant risk of injury or even death to the laborers below. In addition, there can be as much as a ten to twelve-foot drop from the surface of the road, and the upper end of the drop inlet, to the bottom of the collection box on which the drop inlet is mounted. A fall from such a height can cause severe injuries to persons who might inadvertently fall into the inlet, especially as the open end of the inlet becomes obscured by dirt and other debris. The danger of an exposed, i.e. open, ten to twelve-foot drop inlet is especially great for children who might play around the area and are more likely to be curious and to inadvertently fall in and become trapped within the drainage pipes.
In the past, the open upper ends of the drop inlets generally have been protected with a simple silt fence constructed of a flexible mesh or screen material attached to a series of wooden stakes positioned about the open upper end of the drop inlet. Such an arrangement is illustrated in FIG. 1, which shows in general the known method of enclosing and marking the open end of a drop inlet at construction sites. Such arrangements, however, have not proven satisfactory for preventing dirt and debris from falling into the open end of the drop inlet, and they provide little or no protection against persons inadvertently falling into an open drop inlet, and especially for keeping children out of the inlet.
In fact, as shown in FIG. 2, the known silt fences typically tend to collapse, or be blown down, or washed down over a short period of time. This is due to the fact that the mesh of the silt fence and the stakes holding the silt fence in place are not strong enough to withstand heavy rains and wind, and even less so the force of dirt and debris being pushed against the silt fence by a motor grader or bulldozer as the streets and curbs of the site are graded. Under such weight, as illustrated in FIG. 2, the silt fence generally will collapse, often falling into the open end of the drop inlet itself thus permitting the accumulated dirt and debris being urged or pushed thereagainst to fall into the drop inlet.
Although the simplest solution to this problem would seem to be to completely seal the open end of the drop inlet, this is not feasible in that rain and storm runoff water must be permitted to drain through the storm water drainage system of the development during construction to permit the ground to dry, and to prevent storm water from eroding the work site and carrying soil and debris to adjacent lots or buildings. Also, the construction site must be kept as dry as possible in order to enable the curbs and throats to be poured and the streets to be finished, which cannot otherwise be accomplished if the ground is too wet to support the concrete as it is poured and formed, thus necessitating a good, open drainage system for the site.
Accordingly, it can be seen that a need exists for a device to cover and protect the open upper end of a drop inlet for a storm water drainage system at new construction developments which will prevent silt, dirt and debris from being washed or blown into the inlet, and will also prevent access to the inlet to minimize the risk of accidents due to persons falling or climbing into the open inlet, but which still allows for the free and substantially complete drainage of storm runoff water into the drainage system at the development site.
Briefly described, the present invention comprises a temporary and substantially rigid silt guard and cover for a drop inlet used in a storm water drainage system. The present invention generally is designed for use at construction sites for enclosing the open upper end of a drop inlet of the storm drainage water system of the development during the construction of the streets, curbs, and the construction of the drainage system itself. The silt guard generally is substantially cylindrically shaped, is approximately two to three feet in height, and is formed from a rigid, durable plastic material, and is sized and shaped to fit over and seat upon the upper ends of most conventional drop inlets.
The silt guard typically includes a substantially cylindrical or tubular body portion having an upper end and a lower end. A circular bottom rim is formed about the lower end of the body, slightly overlapping the sides of the body. The bottom rim is approximately 48 to 60 inches in diameter, defining a lower opening in the silt guard, and is adapted to fit over and seat upon the open upper end of a drop inlet. Typically, the bottom rim is flared outwardly to enable the silt guard to adapt to seat on drop inlets of varying sizes and shapes constructions, although it will be understood that the rim also can be formed in other configurations, including being flat. The body portion further includes a series of spaced, vertically extending slats or ribs that extend from the bottom rim and taper inwardly toward the upper end of the body. The slats are spaced from one another to define a series of radially spaced openings or passages there between to enable the flow of water into and through the silt guard while blocking passage of large debris and silt.
The silt guard further includes a top portion that extends upwardly from the body and generally has a substantially smaller diameter than the upper end of the body. The top portion generally is substantially curved or dome shaped and extends vertically and tapers toward the upper end of the body. A series of radially spaced slots or openings also can be formed in the top portion of the silt guard to provide extra pathways for storm runoff water porous to drain into the inlet.
In use, a filter cover or cap formed from a silt screen, mesh or similar porous filtering material is fitted over and covers the silt guard. The cover generally will be sized and shaped to conform to the shape of the silt guard, having a domed top portion that fits over the top portion of the silt guard and a skirt portion that covers the slats of the body portion and overlaps the bottom rim of the silt guard. The filtering material of the top portion of the filter cap also can be painted or dyed a fluorescent color to make it easier to detect to warn of or signal the location of the drop inlet. A ring or support tube further generally is applied at the bottom of the skirt portion, typically being formed from a heavier plastic material. The ring defines a pocket or series of pockets about the bottom of the skirt portion, in which dirt and/or stone is received to help hold the cover on the silt guard.
Alternatively, workers can wrap the body portion of the silt guard with a silt screen or mesh material typically having a width of at least two to three feet in place of the filter cap or cover. The silt screen material is secured to the upper end of the body portion by fasteners, such as screws, or on hooks or similar fastening devices mounted to the upper end of the body. The lower end of the silt screen material is left overlapping the bottom rim of the silt guard by approximately 6 inches and thus overlaps the open upper end of the drop inlet on which the silt guard is mounted.
As dirt is urged against the silt guard, the weight of the dirt further helps hold the silt guard on the inlet and hold the filtering material of the filter cap against the silt guard. The slats or ribs of the body portion provide strength and rigidity to the silt screen material as dirt and debris are pushed thereagainst so as to prevent the collapse of the silt screen material, and thus the passage of the dirt and debris into the drop inlet. The filtering material enables rain and runoff water to pass therethrough and through the openings or passages formed between the slats to enable rainwater, etc. to drain into the drainage system while blocking the passage of silt and debris therethrough.
Once the curbs have been graded and are being poured, workers will dig out the excess dirt from around the silt guard and drop inlet, and the silt guard can be lifted upward and off of the drop inlet to enable the throat to be poured around the drop inlet to finish the drain or manhole. The used filter cover then simply is removed from the silt guard, and the silt guard cleaned of excess dirt and debris leaving it ready for its next use.